Heat insulation means for power tools

ABSTRACT

The invention relates to power tools, for example, a hand operated jig saw, having a housing of heat sensitive plastics material. A heat insulating layer of duroplastics is arranged intermediate the points of contact between said housing and members of the tool which are subject to heat-up during the operation of the tool, especially the bearing means such as a sleeve bearing.

United States Patent H 1 3,695,344

Schnizler, Jr. 1 Oct. 3, 1972 [S4] HEAT INSULATION MEANS FOR [56]References Cited POWER TOOLS UNITED STATES PATENTS [72] Inventor:Albrecht Schnizler, Jr., Nuertingen,

Germany 3,121,313 2/1964 Pratt et al ..3|0/50 3,404,574 /1968 Stelljes143/63 F X [731 Assgmfi Mmbmm 3,533,600 10/1970 Gel-son ..3 10/50 xScum", Mamie". wuertem' 3,4l7,469 12/1968 Cousins et al ..3|0/s0 uxberg, Germany [22] Filed: Aug. 27, 1970 Primary Examiner-Andrew R..luhasz Assistant Examiner-James F. Coan Appl' Attorney-W. G. FasseForeign Application Priority Data [57] ABSTRACT m- 1969 rmany 69 34 5273The invention relates to power tools, for example, a

hand operated jig saw, having a housing of heat sensil Cl 143/63 143/157tive plastics material. A heat insulating layer of du- 3l0/43, 310/5roplastics is arranged intermediate the points of con- [5l] llli. Cl.J32") 1?]08 t b t aid hou ing and members of the tool [58] Field ofSearch ..3lO/50, 43, 64, 143/60,

143/68 R, 68 E, 68 F, 70, 71, 84 F, 84 J, l56, [56 A, 157 C; /69, 134,135, I36,

which are subject to heat-up during the operation of the tool,especially the bearing means such as a sleeve bearing.

5 Claims, 9 Drawing Figures PATENTEUuma m2 SHEET 2 BF 2 INVENTORALBRECHTSOWVIZLE Q ATTORNEY HEAT INSULATION MEANS FOR POWER TOOLS Thepresent invention relates to a power tool, more especially, to a handoperated power tool such as a jig saw. Such power tool comprises ahousing made of heat sensitive material, for example, plastics. Themembers of the tool which during its operation are subject to beingheated, for example, the bearings and the like are supported in thehousing and held in a fixed position in such housing.

Especially electrically driven hand operated tools are constructed so asto have a longitudinally divided housing because this results in aninexpensive production since the two housing portions or shells may bemade of thermoplastics material in an injection molding process. Theindividual members of the tool, such as the motor, the armatur, thebearings, the gears. and switches and so on are assembled into the toolby inserting them into one of the shells of the housing where thesemembers are fixed in their desired position by means of ribs provided onthe inside surface of the housing shells. Thus, the tool members arefixed securely in their positions when both shells are secured to eachother, for example, by means of screws.

However, thermoplastics material have a tendency to assume a plasticstate or condition already at relatively low temperatures. As a result,such tool members as gears and bearings and the like which dissipate asubstantial amount of heat cannot be retained in fixed positions in thehousing shells because the latter are deformed by said dissipated heat.

ln view of the foregoing it is the main object of the invention, toovercome the outlined drawbacks.

It is yet another object of the invention to avoid the deformation ofthe housing shells by the heat developed by individual tool members sothat such members will be retained in their fixed positions in thehousing shells. According to the invention there is provided a powertool in which the parts or members which are subject to heating duringthe operation or which develop heat during the operation are separatedfrom the heat sensitive housing by means of a heat insulating layer.Especially, the parts which are subject to heating or which develop heatduring the operation are surrounded by a heat insulating layer at leastin those areas in which said members are in contact with the heatsensitive housing. It is suitable to provide said members with the heatinsulating layer by inserting the members into a mold and applying theheat insulating layer to the members under pressure whereby either themembers are covered completely or partially.

A material suitable for use as an insulating layer according to theinvention is a so called duroplastics material which will retain itsgiven shape even at elevated temperatures such as will occurr due to theheat generated in a bearing or a similar tool member. Furthermore, theseduroplastics have a very low conductivity. Therefore, the heat generatedin the tool member, such as a bearing, is prevented from passing to thehousing shells made of thermoplastics material. The constructionaccording to the invention is especially suitable for use in connectionwith a jig saw comprising a sleeve bearing guide member subject tosubstantial heating during operation. In one embodiment of the inventionthe sleeve bearing guide member of a jig saw is adapted for contactingthe housing in a bear ing area and in a guide area. The bearing area iscompletely surrounded by a duroplastics material whereas the guide areais surrounded on at least two sides by such a duroplastics heatinsulating material. In order to assure a secure retaining of themembers surrounded by said duroplastics material in the thermoplasticshousing ribs are provided in the duroplastics insulating layer. Thehousing shells are provided with correspondingly shaped recesses intowhich said ribs fit in a form closing manner.

In order that the invention may be clearly understood, it will now bedescribed, by way of example, with reference to the accompanyingdrawings, wherein:

FIG. 1 illustrates a partial longitudinal sectional view through ajigsaw;

FIG. 2 is a front face view of a jig saw as seen in the direction of thearrow ll in FIG. 1; and

FIGS. 3 to 9 illustrate different views and sections through the sleevebearing guide member of the jig saw.

The power tool illustrated for example as a jig saw, comprises a driveshaft 1 which drives a gear 3 supported on an axle 2, by means of aneccentric stud 4 supported in said gear 3. The eccentric stud 4 drives asaw blade 7 up and down in a sleeve bearing guide member 8 by means of asliding member 5 and a driver rod 6. The sliding member 5 grips into aguide member 6' rigidly connected to the driver rod 6. The sleevebearing guide member 8 is subject to being heated due to the heatgenerated during the operation of the jig saw as a result of thefriction between the gliding members, more specifically, the frictionbetween the guide member 6' and the glide path 9 in the guide area [0 aswell as the friction of the driver rod 6 in the bearing area 11.

Substantially, all of the moving parts except the saw blades 7 aresurrounded by housing 12 which comprises two housing shells 13 and 14each shell forming one half of the housing. The two shells are connectedto each other along a plane represented by a line 15 (FIG. 2). Suchconnection may, for example, be by means of screws and is well known inthe art.

The inside of the shells l3, 14 are provided with ribs 20 and shoulders21 into which the tool members, such as the bearings, switch means, thearmatur and especially the sleeve bearing guide member 8, are insertedand rigidly held. ln order to prevent that the sleeve bearing guidemember 8 dissipates its heat directly to the housing shells l3 and [4made of thermoplastics material, the invention provides a heat barrieror heat insulating layer 16 between the sleeve bearing guide member 8and the housing II. The heat barrier 16 is made of duroplasticssynthetic material which is not affected in its properties, especiallyin its shape retaining properties by the heat occurring around thesleeve bearing guide member 8 and which therefore retains its shape.

As may be seen from FIGS. 3 to 9 the sleeve bearing guide member 8 whichwill normally be a metal member is surrounded by the heat barrier 16that is by the duroplastics synthetic material, which is applied to thesleeve bearing guide member 8 by inserting it into a mold and applyingthe duroplastics material under pressure. It will be noted from H6. 3 to9 that the heat barrier 16 is provided especially at those points orareas in which the tool members are in contact with the housing shellsl3 and 14, more specifically, where the entire sleeve bearing guidemember 8 is held in the housing 12. At the top of FIGS. 3 and 4 there isshown a guiding area 10 and at the lower portion of FIGS. 3 and 4 thereis shown a bearing or supporting area 11. It will be noted that the heatbarrier or layer 16 is provided in the guiding area 10 as well as in thebearing area 11 with ribs 17 and 18 which assure the precise position ofthe sleeve bearing guide member 8 in the housing shells I3 and 14. Theglidepath 9 is not covered by the heat barrier 16. This applies alsowith regard to the back side 19 which is not in contact with the housing12 thereby providing a spacing between the housing and the heat barrier16 so that any generated heat is easily removed as by an air current.

With regard to FIGS. 6 and 7 it will be noted that in the guiding area10 where the barrier I6 is in contact with the rib 20 and the shoulder21 of the housing shells l3 and [4, the heat barrier 16 surrounds thesleeve bearing guide member on three sides. However, a heat barrieradjacent to only two sides of the guide member will also be suflicient.In this connection it should be mentioned that the sectional lines whichin FIGS. 3 and 4 are identified by roman numerals lV-lV and VII Vll,refer to the Figure having the respective arabic numerals 4 and 7.

The advantages achieved by the invention reside especially in the factthat the simple and inexpensive construction comprising a two shellthermoplastics housing may be retained without any danger that partssubject to heat generation might cause a deformation, especially of thethe housing. As a result, the precisely fixed position of the bearingsand similar parts or tool members is assured and abnormal wear and tearis avoided. Accordingly, the useful life of the power tool issubstantial increased and this has been achieved by surprisingly simpleand expeditious means.

Examples of thermoplastic materials of which the present housing shellscould be made are synthetic materials such as poly-amides,poly-ethylene, poly-carbonates, and mixed poly-merisates ofstyrene-acryl- 4 nitriles.

The heat insulating layer as provided according to the invention couldfor example be made of duroplastic materials such as phenolic resins,expoxy resins and unsaturated poly-ester-resins.

The invention is" not intended to be limited by the describedembodiments nor to the example materials used. it is intended to coverall modifications and equivalents within the scope of the appendedclaims.

What I claim is:

l. A power tool comprising a housing made of heat sensitive material.means supported in said housing and subject to heating by increasedtemperatures during the operation of the power tool, and means made ofduroplastic synthetic material for heat insulating said supported heatsubjected means from said housing whereby the heat subjected means arekept out 'of direct contact with the housing.

2. The power tool according to claim 1, wherein said heat sensitivehousing comprises supporting means in contact with said heat insulatingmeans located at least at predetermined points between said housingsupporting means and the means subject to heating.

3. The power tool according to claim 2, wherein said heat insulatingmeans are provided in the form of a layer pressed about said supportedmeans at said points.

4. The power tool according to claim 1, wherein said housing of heatsensitive material comprises two shells, said supported means comprisingjig saw means including a sleeve bearing member having a supporting areaand a guiding area, said heat insulating means being arranged tosurround the supporting area of the sleeve bearing member and to contactsaid guiding area at least at two sides thereof.

5. The power tool according to claim '4; wherein said heat insulatingmeans comprise ribs for fixing the position of said heat insulatingmeans in said housing of heat sensitive material.

* 1' i i l

1. A power tool comprising a housing made of heat sensitive material,means supported in said housing and subject to heating by increasedtemperatures during the operation of the power tool, and means made ofduroplastic synthetic material for heat insulating said supported heatsubjected means from said housing whereby the heat subjected means arekept out of direct contact with the housing.
 2. The power tool accordingto claim 1, wherein said heat sensitive housing comprises supportingmeans in contact with said heat insulating means located at least atpredetermined points between said housing supporting means and the meanssubject to heating.
 3. The power tool according to claim 2, wherein saidheat insulating means are provided in the form of a layer pressed aboutsaid supported means at said points.
 4. The power tool according toclaim 1, wherein said housing of heat sensitive material comprises twoshells, said supported means comprising jig saw means including a sleevebearing member having a supporting area and a guiding area, said heatinsulating means being arranged to surround the supporting area of thesleeve bearing member and to contact said guiding area at least at twosides thereof.
 5. The power tool according to claim 4; wherein said heatinsulating means comprise ribs for fixing the position of said heatinsulating means in said housing of heat sensitive material.